The present invention is a control system and associated method for use with artificial limb substitutes. In particular, the present invention is a biomimetic controller for transducing volitional muscle, tendon, and ligament motions into signals that control either real or virtual movements of external limbs. It is intended for persons who either lack functional limbs, such as hands, or for those who wish to control manual devices without using their hands.
In contrast to the dexterous manipulations performed by computer-controlled robotic hands with many-degrees of freedom, human-operated prosthetic hands function much as they did over a century ago, by single-jointed grasping. This dichotomy underscores the urgent and as yet unmet challenge of developing a versatile interface between human and machine. Specifically, the interface must accurately receive and transmit human volitional commands independently to each finger.
Present interfaces for prosthetic hands, whose function is primarily prehension, are either body powered, or myoelectric, or a combination thereof Standard body powered prostheses are controlled by a harness attached to the shoulders, that transduces shoulder flexion-extension and abduction/adduction into opening-closing of the hand. While harness-type controllers have proven reliable and robust for thousands of amputees over decades, their versatility is limited by the number of independent control motions practically possible: one. Myoelectric controllers may eventually offer more degrees of freedom (DOF), but this number is limited by the ability of the user to learn the use of non-natural movements to activate hand motions and the ability of the controller to decode the resulting electromyographic (EMG) signals. Due at least in part to these limitations, myoelectric controllers still provide only one practical DOF, directed by flexion-extension of arm muscles.
A potentially high degree of versatility has been experimentally introduced into body-powered controllers that directly attach prosthetic finger actuators to muscles whose tendons have been surgically exteriorized. However, the immediate utility of these controllers is limited by problems of tissue integration, pathological risk, and cost.
An ideal interface would sense, decode and transmit volitional signals from the original motoneuron pathways to actuators on the prosthesis. Direct hook-up to nerves transmitting biological signals thus may be the ultimate method for controlling the bionic hand, but the problems of long-term recording, as well as decoding complex spike trains, have proven formidable.
The closest alternative to biological control by nerves is biomimetic control based on the hand and finger actuators that remain intact in the residual limb. These include the extrinsic muscles and tendons controlling flexion of the metacarpal-phalangeal joints. While myoelectric recording from the individual finger-associated muscles, i.e. separate branches of the flexor digitorum, would be cumbersome, sensing their associated tendon motions appears to be more direct, since tendons directly move the fingers. Accordingly, a control system based on sensors of superficial tendon movements is desirable. The sensor should be well matched to tissue compliance and have a dynamic response range spanning the tendon force output.
A sensor system having these characteristics is part of this invention and consists of tendon-activated-pneumatic (TAP) foam sensors apposed between the skin and a hard external socket enclosing the limb. TAP sensors can transduce volitional motions of intact muscles, tendons, ligaments or tendon residua into control signals for mechanical fingers to produce finger tapping, grasping, and independently graded finger forces.
The simplest voluntary movements require activation of many muscles, and finger motions are especially complex, since each finger is controlled by activities of several dispersed muscle groups. In contrast, single extrinsic tendons directly move individual fingers. This relative simplicity of tendons and/or closely associated muscles makes them attractive controllers for hand prostheses.
It is an object of the present invention to provide a control system for use with a prosthetic or orthotic device comprising sensor means for sensing and generating at least one signal in response to volitional movement of a muscle or tendon intended to cause an associated desired movement of a bodily limb; electronic interface means for analyzing at least one signal and sending a corresponding control signal to the receiving/actuator device indicative of the desired movement of the body part.
It is a further object to provide a method for controlling the movement of an upper extremity prosthesis or orthosis in response to volitional movement of associated tendons, muscles, or ligaments corresponding to the upper extremity comprising: providing a catalog of sensed motion data corresponding to a range of motion and proportional force associated with the upper extremity; disposing and aligning a plurality of sensors onto an arm member at locations corresponding to active superficial tendons associated with extrinsic finger muscles, wherein each sensor operates to sense volitional movement of an associated tendon or muscle for causing movement of the corresponding finger and generating a deformation that causes a signal in response thereto; coupling the plurality of sensors to an electronic interface means for analyzing the signals and comparing with the catalog of motion data to generate a corresponding pattern of control signals for output to the associated upper extremity prosthesis or orthosis indicative of a desired movement.
It is a further object to provide a method for controlling the movement of a simulated hand and fingers in response to volitional movement of associated tendons, muscles, or ligaments corresponding to the hand and fingers comprising all aspects mentioned above.
It is a further object to provide a method for interfacing with a computer without a keyboard, using all aspects mentioned above.
It is a further object to provide a method for interfacing with keyboards, electronic musical instruments, games, and toys using all aspects mentioned above.